Well, Diablo Cody has never been shy about being divisive. Juno, Jennifer’s Body, and Young Adult are both adored and reviled (I’m usually in the latter camp). And before Tully even came out, it has been criticized and questioned for its depiction of a mother struggling with, well, every goddamn aspect of motherhood.

Like Cody and director Jason Reitman’s previous partnerships (in particular Young Adult, which also starred Charlize Theron), Tully’s characters are often consumed by self-loathing, a rejection of social niceties, and almost a maniacal kind of id. Compared with other films about parenthood, Tully is atypical, while for these filmmakers, it’s more of the same.

Theron stars as Marlo, a woman in her early 40s who is pregnant (unplanned) with her third child; much is made of how she and husband Drew (Ron Livingston) rarely have sex, so the child certainly isn’t intentional. But is anything in their life really intentional? Every morning getting their two children out the door for school is a struggle. Every conversation between Marlo and Drew dips into passive-aggressiveness or disinterest. And it’s clear that Marlo views this final child not with excitement, but resentment. She doesn’t want to know if the child is a boy or a girl. She jokes with her daughter about killing herself. When she runs into an old girlfriend, her description of her life as “nothing’s changed” is exhaustively resigned and fully sarcastic. She views the pregnancy as something that is happening to her, not something she’s involved in.

Is Marlo happy? When she and Drew go visit Marlo’s aggressively wealthy brother Craig (Mark Duplass), with his absurdly huge house and live-in hipster nanny and tiki bar, he mentions not wanting what happened with her last pregnancy to happen again. There are hints here of things people don’t want to talk about — no one comes straight out and says that Marlo and Drew’s son may have autism, although her son’s behavior is something that often causes Marlo’s meltdowns — and one of those avoidances is asking Marlo how she’s truly feeling.

The only person who seems to care is Tully (Mackenzie Davis), a night nanny that Craig hires for Marlo as a way to help her cope. Tully is in her 20s, free-spirited and curious and energetic, and her presence helps Marlo feel alive again. She draws the older woman out of her haze, so Marlo is not only more engaged when Tully is around, but more present overall — for her husband, for her kids, for herself.

What Cody often does with her characters is form women who are equally relatable and infuriating, and adding in motherhood to the mix with Tully is another complicated layer. How you view Marlo as a protagonist may be affected by how you view motherhood: Are children blessings or burdens? Can they be both at the same time? Are they responsible for your happiness? Is your spouse or your partner? Are you? Does your happiness supersede your family’s? What is the defining identity in your life — is it what you desire to do for yourself, or what you’re expected to provide for others?

Tully mines those questions while depicting Marlo’s layers of unhappiness and postpartum depression, and the film applies a mixture of emotional fragility and spontaneous crassness and vulgarity that we’ve come to expect from Cody and Reitman when they work together. That combination is familiar, and in delivering it, Theron is fantastic. There are so many moments where she is silently devastating — the detached look on her face when her third child is finally born and her labor is over — and others where you spot the woman she used to be, feisty and adventurous. She and Davis are great together, and the contrast between them, one so guarded and so worn-down and the other so bright and bubbly, is the main emotional through-line of the film. What is problematic, though, are the film’s final few minutes, which introduce a major character detail and then somewhat sidestep its resolution (spoiler alert); the film considers weighty issues until the very end and then refuses to delve into answers.

Maybe that’s the point, although it’s somewhat unfulfilling: If who you were is who you still are is an existential question Tully raises with Theron as its center and forces you to wonder for yourself, too, whether you’re a mother or not.

Roxana Hadadi is a Staff Contributor for Pajiba. You can follow her on Twitter.